EVALUATION OF ECC BASED ON UPV AND REBOUND HAMMER TESTS

Recently, many studies have been conducted to investigate the hardened properties of concrete which replaces fiber with coarse aggregate. Thus, this has led to a result of discussing benefits and problems of Engineered Cementitious Composite (ECC) with comparison to conventional concrete mixtures. There are various purposes of ECC in the construction industry. Thus, an in depth evaluation of ECC mixtures to establish valid relationships by using non-destructive tests, namely, rebound hammer (RH) and ultrasonic pulse velocity (UPV). Twenty mixtures with different Nano-Silica content percentages and PVA Fiber content percentages were prepared, casted and tested using RH and UPV at different curing ages. Six cubes are casted for each mixture to be evaluated for the periods of 7 and 28 days. The average of the results for each test are calculated, and recorded to be analyzed using Response Surface Methodology (RSM) by Design Expert software. The models were proposed to validate and predict the connection between compressive strength with UPV and rebound number (RN) for ECC mixtures with duration of 7 and 28 days, respectively. These models will ease the work of predicting the content of the variables (in this case, the variables are Nano-Silica % and PVA fiber %) in relation to the response (which are, Rebound Number, Ultrasonic Pulse Velocity and Compressive Strength). From the results obtained, it’s noticed that rebound number decreases slightly with the increase of Nano-Silica percentage and the same goes to the value of the ultrasonic pulse velocity test, while the compressive strength of ECC samples increases with the increment of Nano-Silica content, but when the Nano-Silica percentage goes higher than 3% the compressive strength drops down due to the effect of the particles of Nano-Silica. After the results are obtained, they will be analyzed using Response Surface Methodology by Design Expert Software to develop specific equations as models where these equations are designed by the software to calculate the values of rebound number, ultrasonic pulse velocity and compressive strength. Hence, the developed models will assist the researcher in reduction of the experimental works.